In an optical transport network (OTN) which is a wide-area optical transport network with a large capacity, client signals based on various standards such as synchronous digital hierarchy (SDH), Ethernet (registered trademark) and the like are accommodated and transmitted.
In recent years, traffic of client signals has increased remarkably and thus OTNs have been standardized to cope with an increase in speed (for example, see Non-Patent Document 1). At present, optical channel transport unit-Cn (OTUCn) (where Cn denotes 100G×n) which is an OTN technique over 100 G (B100 G, where G is gigabits per second) is being studied (for example, see Non-Patent Document 2).
In OTUCn, a transmission capacity of one optical channel is a frequency band wider ha that in the conventional OTU. However, it is difficult to achieve an increase in capacity by extending single carrier transmission in a frequency band of one optical channel as before due to a relation with an operating speed of an electronic circuit which is used for an optical signal transceiver. Therefore, in OTUCn, an increase in capacity is realized by multicarrier transmission using a plurality of optical subcarriers in the frequency band of one optical channel.